Diisocyanato aromatic compounds



United States Patent 3,105,845 DIISOCYANATO AROMATIC COMIOUNDS Lloyd C.Fetterly, Oakland, David 0. Collamer, Grinda, and Curtis W. Smith,Berkeley, Calif., assignors to $hell Oil Company, a corporation ofDelaware No Drawing. Original appiicaticn Sept. 14, 1954, Ser. No.456,078, now Patent No. 3,089,862, dated May 14, 1963. Divided and thisapplication Dec. 15, 1958, Ser- No. 780,214

6 Claims. (Cl. 260-453) This invention relates to a new class ofdiisocyan-atoand diisothiocyanato-substituted aromatic compounds. Morespecifically, the invention rel-ates to novel polysubstituted compoundsof this type having especially advantageons properties and to theutilization of these new compounds.

The invention provides new and useful compounds which can be describedas compounds having a benzene ring to which two, and only two,substituents of the group consisting of the isocy-anato andisothi'ocyanato radicals are directly attached and having an alkyl groupin each of the positions ortho to said functional groups. Due to thischaracteristic structural arrangement of the groups attached to thebenzene ring, the novel diisocyanates, diisothiocyanates andisocyanatoisothiocyanates have unexpected beneficial properties whichmake them particularly adapted for important commercial applications.

Organic polyisocyanates and polyisothiocyanate-s are known to be usefulin the preparation of polymeric materials due to their ability to reactwith hydroxy, carboxyl, amine and like groups containing active hydrogenatoms. The use of these compounds as curing or vulcanizing agents for avariety of different types of polymers is described, for example, in US.Patent 2,381,063. In

Industrial and Engineering Chemistry, vol. 46, pages 1498-1507 (1954),other polymers from diisocyanates and polyols are described. It ispointed out in US. Patent 2,625,535 that careful control is essential inorder to obtain products of this type having advantageous physicalproperties. One thing which contributes to the difficulty in obtainingproducts of the most desirable properties in such reactions is thetendency toward excessive cross-linking between polymer molecules whichhas been found to occur with the reactants heretofore employed. It is onthis account that it has been found essential to use compounds with notmore than two reactive isocyanato or isothiocyan-ato groups in themolecule for the preparation of polymers having desirable rubber-likeproperties. Even when using this type of compound, difficulties havebeen encountered due to the ease with which the initial reaction productcan undergo further reaction with the organic diisocyanates anddiisothiocyanates previously available. Thus, for example, when reactinga diisocyanate with a hydroxy, oarboxyl, or amino group, the respectiveproducts will contain urethane link-ages, while the analogous thiogroups,

are formed when using a diisothiocyanate. All of these groups containactive hydrogen atoms which readily react with another molecule of thediisocyanate or diisothiocyanate. This can lead to excessivecross-linking which often makes the product difiicult to process orotherwise gives it less desirable properties. The compounds of thepresent invention, being less subject to such undesirable furtherreaction under these circumstances, facilitate production of polymericproducts of improved properties.

The new compounds of the invention can be divided into subclassesaccording to the relative positions of the two isocy-anato and/ orisothiocyanato groups in the molecule. The compounds which have beenfound to be most advantageous for the production of linear polymers arethose having the two N=(,=X groups (X being oxygen or sulfur) attachedto" non-adjacent ring carbon atoms. Those inwhich the N=O=X groups arein ortho position to each other are much less useful as polymer linkingagents or the like than the new compounds of the invention which havethese groups further removed from each other. Especially preferredcompounds are those having the two N=( X groups linked to the benzenering in para position to each other. The subclasses of the new compoundsare characterized respectively by the following general formulae:

and

wherein X represents an oxygen or a sulfur atom, R represents an alkylradical, and R represents a hydrogen atom or an alkyl radical.

Examples of the preferred alkyl hydrocarbon radicals of 1 to 18 carbonatoms represented by R and/or by R include such straight chain alkylradicals as the methyl, ethyl, butyl, amyl, octyl, lauryl and stearylradicals,' and such branched-chain alkyl radicals as the isopropyl,secondary, tertiary, and isobutyl, 2-ethyl hexyl, and tetramethyl octylradicals.

The tetraalkyl-substituted benzene diisocyanates and dii-sothiocyanateshaving the functional groups in meta or para position form an especiallypreferred subgroup of the compounds of the invention. This subgroup ofcompounds has the double advantage of not only sharing the unexpecteddesirable properties which characterize the class of new compound-s as awhole but also having special advantages of its own while furthermorebeing readily synthesized in high yields as pure or substantially pureproducts uncontaminated by undesirable isomers. Among the simplermembers of this subgroup are, for example,

Isodurene diisocyanate 0H3 c ing Isodurene diisothiocyanateIsothiocyanatoisodureneisocyanate CH; CH;

C a -N=O=S l =C=N CH Durene diisocyanate 0=c=N- -N=0=o l 1 CH3 CH3Durene dith-ioisocyanate (IJH; (III-l; s=o=r :/N=C=S I CH3 CHIsothiocyanatodureneisocyanate (3H3 (EH3 S=C=N -N=o=o CH3 CH3 Exemplaryof the corresponding higher alkyl compounds of this advantageoussubgroup of the new compounds of the invention "are, for instance:1,2,3-trimethyl- 5-ethyl-4,fi-diisocyanatobenzene;1,3-dimethyl-2,5-diethyl- 4,6-diisothiocyanatobenzene;1-methyl-2-ethyl-3,5 diisopropyl-4,fi-diisocyanatobenzene;2,6-dimethyl-3,5 ditertiarybutyl-1,4-diisocyanatobenzene;2,5-diethyl-3,6-diisopropyl-1,4-diisothiocyanatobenzene;2-methyl-3-ethyl-5-isobutyl-o-hexyl-l,4-diisocyanatobenzene; and2,3,5,-trimethyl- 6-decyl-l-isocyanato-4-isothiocyanatobenzene.

With all the new compounds having the two groups in para-positions onthe same benzene ring, it is necessary that the remaining four positionsbe occupied. When the N=CL=X groups are in meta position to each other,only the three positions need be occupied. Typical of the new compoundsof this subgroup are the follow ing:

l,3,S-trimethyl-Z,4 diisocyanatobenzene and their higher alkyl isomerssuch as l-decyl-3,5-diethyl- 2,4-diisocyanatobenzene;1-isopropyl-3-methyl-5-cthyl-2,4- diisccyanatobenzene; 1-allyl-3,5dimethyl 2,4 diisocya- 4 natobenzene; lamyl-3-(2-ethylhexyl)-5-methyl-2,4-diisothiocyanatobenzene; and thelike.

The new compounds of the invention can be produced in various ways. Onesuitable method utilizes as starting materials the correspondingaromatic primary diarnines having the ring carbon atoms orthoto theamino groups occupied by alkyl groups, which are readily available orout the reaction in an analogous manner using thiophosgene instead ofphosgene for reaction with the chosen aromatic primary diamine. can alsobe produced successfully by reacting the corresponding aromatic amineswith carbon bisulfide, ammonium hydroxide and lead nitrate. Also, arylthioureas decompose thermally in a solvent to give aryl isothiocymatesand ammonia.

corresponding diisothiocyanates with mercurous oxide, preferably usingnot more than one mole of the oxide per mole of the diisothiocyanate soas to convert one of the;

isothiocyanate groups to an isocyanate group without converting theother isothiocyanate group. The products of this reaction are mixturesof diisocyanate, diisothiocyanate and mixed isocyanate-isothiocyanate.These compounds can be separated by distillation, or can usually. be iused successfully without separation.

The following examples illustrate the production of new compounds of theinvention by the foregoing meth ods, but it will be understood thatother methods can be used.

Example I Durene diisocyanate was prepared by dissolving du-renediaminein anhydrous ohlorobenze-ne in a stirred reactor provided With a refluxcondenser and heating coil, adding anhydrous hydrogen chloride toconvert the diamine to the dihydnochloride, and heating the resultingsuspension at C. with vigorous stirring While feeding in phosgene inexcess over a period of 2.5 hours. The mixture was then refluxed at 132C. for half an hour to drive off hydrogen chloride from the carb-amylchloride. The first cnop of white crystals was 57% of the theoreticalamount of durene diisocyanate and melted at 113.5 114 C. Vacuumevaporation of the mother liquor gave a light tan solid (43% of thetheoretical yield) melting at 112 C. which Was recrystallized fromSkellysolve B as white crystals melting at 113.51l4 C. for a 94% totalyield of durenediisocyanate based upon the durene diam-inc employed.

Example II Du-rene diisothiocyanate is produced by reaction as inExample I, using thiophosgene instead of phosgene.

Example III Prehnitene diisocyanate is produced by reacting prehnitenediarnine dihydrochloride with phosgene under conditions of Example I.

Example IV Isodurene diisocy-anate is produced, by reacting'under, theconditions of Example I, isodurene diamine dihydrorobenzene solution at1l0-130 C. and recovering the crystalline product as in Example I.

Example VI Mesitylene diisothiocyanate is produced by reacting The newdiis-o thiocyanates.

The mixed isocyanato isothiocy anato compounds are readily obtained byheating the the mesitylene diamine dihydrochloride with thiophosgeneunder the conditions of Example V.

The new compounds are valuable intermediate in the production of otheruseful compounds. By reaction with hydroxy compounds they form usefulcarbamates, for example. Thus, Warming the durene diisocyanate ofExample I with excess ethyl alcohol gave the solid durene urethane CH3CH3 I l CH3 CH3 melting point 274 C. Corresponding products fromisopropyl, allyl, tertiary butyl and decyl alcohols are also useful newcompounds. In general, the monoand dicarbamates of the new diisocyanatesand diisothiocyanates with monohydric alcohols, preferably aliphaticalcohols, of l to 12 carbon atoms per molecule are valuable products ofthe invention.

Especially important new compositions of the invention are the polymerswhich are obtainable from the new diisocyanates and diisothiocyanates,particularly the polyurethanes which can be produced by reaction withpolyols. Polyurethanes having desirable properties can, for example, beobtained by warming the new diisocyanates and diisothiocyanates withethylene glycol, propylene glycol, trimethylene glycol, and the like.For instance, durene diisocyanate warmed with the stoichiometric amountof 1,4-butanediol gives a high melting polymer, while similar reactionwith 1,5-pentanediol gives a lower melting polymer. Polymers of moreadvantageous properties are produced by similarly reacting dihydricalcohols having the carbinol groups separated by at least 4 carbonatoms, more preferably 6 to 22 carbon atoms. Typical examples of diolsof this type which form valuable polymers with the new diisocyanates anddiisothiocyanates are 1,8-octanediol, 1,10-decanediol, 1,l6-hexadecanediol and 1,20-eicosanediol. In preparing polymers of thiskind one can use mole ratios of the new ortho alkyl-substituteddiisocyanates and diisothiocyanates to diol of 0.7:1 to 13:1 and obtainuseful linear products, but we prefer to use these compounds in aboutchemical equivalent proportions or a small excess up to about 10 molepercent of diol.

Another useful type of polyol which can be employed in producingpolymers with the new compounds of the invention are the polyhydroxyethers, particularly the polyalkylene glycols such, for instance, as thepolyethylene glycols having 2 to 20 or more ethylene groups permolecule, the related polypropylene, polybutylene and like glycols.

Especially advantageous polymeric products are obtained by reacting thenew aromatic diisocyanates and diisothiocyanates with polyesters havingat least two hydroxy groups in the molecule. One or more of thesehydroxy groups can be carboxyl hydroxy groups, but more preferably atleast one, and most preferably at least two, are carbinol hydroxygroups. These polyesters can be produced by known methods. They areprepared, for example, by heating one or more dibasic carboxylic acidswith a glycol or mixture of glycols. Ordinarily no catalyst is necessarybut the condensation can be accelerated by using p-toluenesulfonic acid,zinc or stannic chloride, hydrochloric acid, calcium acetate or thelike. These catalysts are usually employed in amounts of the order ofabout 0.1% to by weight of the reactants. The proportion of dibasic acidto glycol can be varied widely. Generally, the acids are reacted withabout equimolar amounts to 50% excess of glycol, but excess dibasic acidcan also be used in the reaction. It is preferred as a rule to use molarratios of acid to glycol within the range of 1:1.3 to 1.1:1. In mostcases temperatures in the range of about 100 C. to 300 C. aresatisfactory and, most preferably, the water formed in the reaction isremoved as fast as it is produced.

Any dibasic carboxylic acid can be used in preparing the polyesterswhich are reacted with the new diisocyanates or diisothiocyanates of theinvention. Representatives examples are succinic, adipic, glutaric,sebacic, tartaric, terephthalic, beta-methyladipic, octadecylsuccinic,1,20-eicosanedioic and like acids. Preferably saturated dicarboxylicacids having the carboxyl groups attached to terminal carbon atoms areused. Any of the previous mentioned glycols can be used for condensationwith these dibasic acids in making polyesters reactive with the newcompounds. pylene glycol, diand tri-ethylene glycols, pentamethyleneglycol, dodecamethylene glycol, glycerine beta-monomethyl ether,thiodiglycol, glycerol monoacetate, are typical of the dihydroxycompounds which can be successfully used. It is often advantageous toemploy a mixture of diols in preparing the polyesters. For instance, 75mole percent ethylene glycol and 25 mole percent propylene glycol inabout 20% excess condensed with adipic acid, or mole percent ethyleneglycol and 20 mole percent of hexamethylene glycol with mole percent ofsebacic acid, give polyesters which are useful for reaction with thesubstituted aromatic diisocyanates and diisothiocyanates of theinvention. In general, we prefer to use dicarboxylic acids and glycolswhich contain not more than 20 carbon atoms per molecule; mostpreferably, acids of 6 to 12 carbon atoms are used with glycols having 2to 8 carbon atoms per molecule.

Instead of the foregoing polyesters, polyester amides such as are formedby condensing the foregoing dibasic carboxylic acids with a mixture ofone or more glycols and an amino alcohol or diamine, or both, are usefulin forming polymeric products with the new substituted aromaticdiisocyanates .and diisothiocyanates. Suitable amino alcohols are theprimary and secondary amino-substituted alcohols, for example,ethanolamine, 3-amino-propanol, S-amino-pentanol, 8-amino-octanol,10-amino-decanol, l2- =arnino-dodecanol, N-ethyl-ethanolamine, etc.Representative of the diamines are, for instance, ethylene diamine,tetramethylene diamine, hexamethylene diamine, 1,6-diamino-nonane,2,10-diamino-dodecane, ethyl aminopropylamine, 2,2-diaminoethyl ether,piperazine and the like. These polyesteramides can be prepared byreaction, without need for acid catalysts, under the same conditions asare used in producing the previously described polyesters. Preferablynot more than one-third of the reactive hydroxyl and amino groups in themixture condensed with the dicarboxylic acid are amino groups and, morepreferably, only about 5% to 15% of such groups are amino groups.

The reaction of the polyols and polyesteramides of the types describedwith the substituted aromatic diisocyanates and diisothiocyanates,having all positions ortho to the isocyanato and isothiocyanato groupsoccupied, can be carried out in a variety of ways. Ordinarily thereaction is quite rapid at relatively low temperatures, simple warmingof the reactants being sufficient to bring about substantial reaction inmost cases. In general, temperatures of about 40 to 250 C. can be used,but it is preferred to employ temperatures below about 100 C. Thereaction is carried out in the liquid phase with or without solvents ordiluents. The preferred solvents or diluents are inert liquids at thechosen operating temperature and pressure. Reaction times of the orderof 2 or 3 minutes or less up to an hour or more can be used. It is oftenadvantageous to carry out the reaction under a blanket of inert gas suchas nitrogen, carbon dioxide, ethane, etc. Atmospheric, superatmospherioor subatmospheric pressure can be used.

The proportions in which the new diisocyanates and diisothiocyanates areemployed relative to the polyol or polyols can be varied widely.Chemical equivalent amounts are often advantageous but an excess ofeither re- Ethylene glycol, proactant in amounts .as high as 100% hasbeen found satisfactory depending upon the nature of the polymer whichis desired. Higher proportions of diisocyanate or diisothiocyanate or ofpolyol can be used. Depending upon the proportions used, new polymerscan be produced which are hard infusible resinous materials, toughleathery products, fiber-forming compositions, elastic rubberymaterials, and soft waxes or viscous liquids.

The following examples show in more detail how the new polymer productscan be prepared, although it will be understood that other methods ofproducing these polymers can also be used.

Example VII Durene diisocyanate, 40 parts, and 1,4-butanediol, 17 partsby weight, were stirred and heated on a boiling Water bath for aboutone-half hour. The mass increased in viscosity and finally a tough solidpolymer remained. The polymer did not melt at 274 C.

Example .VIII

By the method of Example VII, durene diisothiocyanate prepared by themethod of Example II is reacted with an equal molecular amount of1,10-deca'nediol. When recovered in the same Way, the polyurethanepolymer is much softer and more flexible than the polymer of Example VH.

Example IX Illustrative of the production of durene diisocyanatemodifiedpolyesters is the reaction of 0.95 mole of durene diisocyanate per moleof the polyester produced by condensing a mixture of 60% ethylene glycoland 40% propylene glycol with adipic acid using a 20% mole excess oftotal glycol by melting the Waxy polyester with the durene diisocyanateat about 125 C. After thorough mixing, the produce Was heated for hoursat 145 to obtain to rubbery polymer.

In the same Way excellent products are obtained by substitutingisodurene diisocyanate or prehnitene diisocyanate for the durenediisocya-nate. Due to the presence of substituent groups on the ringcarbon atoms ortho to the isocyanato groups, the NH groups in all theseurethanes are less subject to attack by isocyanates than is the casewhen the diisocya-nates hitherto available are used in the polymers. Asa result, the present products afford a more stable pot-life for thepolymer intermediates and give polymers of especially usefulcharacteristics. For use in the preparation of polymeric materials, thediisocyanato compounds of the invention having the isocyanato groups inpara position on a benzene ring are preferred. Durene diisocyanate is .amost advantageous compound of this type. In all cases the newdiisocyanato-, diisothiocyanatoand isocyanato-thioisocyanato-benzenes ofthe invention which have the most advantageous properties are thosehaving alkyl groups of 1 to 18 carbon atoms and especially thosecontaining only lower alkyl groups of 1 to 5 carbon atoms.

The new polymers can be used alone or with other polymers with orWithout other materials such as pastialkyl-substituted diisocyanato-,diisothiocyanatoand isocyanto-isothiocyanato-benzenes of the inventionwith polyhydroxy compounds are claimed in copending application,

Serial No. 456,078, filed September 14, 1954, of which the presentapplication is a division.

We claim as our invention: Y 1. A dir'unctional polytalkylbenzene havingtwo isocyanato radicals directly attached to nonadjacent ring carbonatoms of the benzene ring as the functional groups and having an alkylradical of '1 to 18 carbon atoms rectly linked to both of the ringcarbon atoms adjacent to the carbon atoms to which said isocyana-toradicals areab tached.

2. A tetraalkylbenzene diisocyanate having the isoeyanato groupsattached to inonadjacent carbon atoms of the ring and having 1 to 18carbon atoms in the alkyl groups.

3. A compound of the following formula:

N=C==O onww om oak -on'g N=G=O 4. Isodurene diisocyanate. 5. A1,3,5-trialkyl-2,4-diisocyanatobenzene having 1 to 18 carbon atoms inthe alkyl groups.

6. An organic diisocyanate of the formula ICH3 IFCO OCN- -CH:

References Cited in the file of this patent FOREIGN PATENTS Germany July5, 1956 Great Britain July 24, 19 57 OTHER REFERENCES Siefkin, W.: Ann.562 (1949), pages 75, 116, 127 and 135.

1. A DIFUNCTIONAL POLYALKYLBENZENE HAVING TWO ISOCYANATO RADICALSDIRECTLY ATTACHED TO NONADJACENT RING CARBON ATOMS OF THE BENZENE RINGAS THE FUNCTIONAL GROUPS AND HAVING AN ALKYL RADICAL OF 1 TO 18 CARBONATOMS DIRECTLY LINKED TO BOTH OF THE RING CARBON ATOMS ADJACENT TO THECARBON ATOMS TO WHICH SAID ISOCYANATO RADICALS ARE ATTACHED.